What are Extensions ?

The GNOME Shell extension project is designed to give a high degree of power to the parts of the GNOME interface managed by the shell, you can extend, change and add features to your desktop by simply loading arbitrary JavaScript and CSS code. This gives developers a way to make many kinds of changes and share those changes with others, without having to patch the original source code and recompile it, and somehow distribute the patched code.

It is a replacement for the "applets" or "widgets" system of GNOME 2. Extensions can add their own items to the top panel, but they can also do much more: adding a custom search provider, for instance. If you lack ideas, see this post.

How to Install GNOME Extensions ?

There is a large collection of extensions on the GNOME Shell Extensions repository website. But you won’t be able to install them if you are using Firefox 52 or later. You will need a Chromium based browser. If you have such a browser :